1. Field of the Invention
The present invention relates to a tool changer for a machine tool. The tool changer detaches and attaches tools through a swinging movement of a turret toward and away from a spindle head.
2. Description of the Related Art
Tool changers that automatically change a tool, attached to a spindle of a machine tool, have conventionally been known. These tool changers have the following configuration. Specifically, a plurality of tools required for machining are set to a plurality of tool holders around a turret. The tool attached to the spindle of the machine tool is automatically changed to a tool designated in accordance with a machining state.
Some such tool changers change the tool in the following manner. Specifically, the designated tool is indexed through a rotating movement of the turret, and the tool attached to the spindle is changed to the indexed tool through a swinging movement of the turret toward and away from the spindle head. The rotating movement of the turret is in rotating directions in the front view of the turret, that is, in the directions of the arrow in FIG. 1. The swinging movement of the turret is in a swinging direction in the side view of the turret, that is, in a movement direction from one of the states in FIG. 2A and in FIG. 2B to the other state.
The tool changer with this configuration moves the tool holder away from the spindle when the machining is in process. Thus, a large machining area can be advantageously ensured.
The following techniques related to the tool changing in the tool changer have been developed. Japanese Patent Application Laid-open No. 2007-290113 discloses the tool changer configured to move the tool holder away from the spindle when the machining is in process. Here, a control is performed so that the turret moves toward the spindle with a swinging movement speed pattern of smoothly slowing down toward an end point of the swing movement, and the turret moves away from the spindle with a swinging movement speed pattern of smoothly speeding up after the swinging movement starts. Thus, the impact on the turret, in the swinging movement, is reduced, whereby a turret mechanism unit prevents the tool holder from receiving a large load. As a result, parts of the turret are prevented from wearing and the tool is prevented from falling off.
Japanese Patent Application Laid-open No. H11-90752 discloses a tool changer that shortens the tool changing time by switching the tool change speed in accordance with the weight of the tool to be changed.
Japanese Patent Application Laid-open No. 2006-272473 discloses a tool changer configured to change a tool by moving a spindle head within a tool changing area. Here, the movement speed of the tool is changed in accordance with the weight of the tool to be changed. Thus, the impact due to mechanical collision caused in the tool changing is reduced, whereby higher reliability is achieved.
The tool changer disclosed in Japanese Patent Application Laid-open No. 2007-290113, which performs tool changing by swinging the turret to move toward and away from the spindle head, controls the speed of the turret moving toward and away from the spindle head. Here, the pattern of the swinging movement is the same regardless of the weight and the arrangement of the tools on the turret. Thus, a certain arrangement of the tools on the turret might result in extremely small impact on the turret in the swinging movement, leaving room for increment in the swing speed. This means that the swinging movement time is longer than necessary, and thus the tool changing time is not sufficiently shortened.
The tool changers disclosed in Japanese Patent Application Laid-open No. H11-90752 and Japanese Patent Application Laid-open No. 2006-272473 change the movement speed in accordance with the weight of the tool in the tool changing. Thus, a shorter tool changing time and lower mechanical impact produced in the tool changing can be achieved. However, the tool changers involve no swinging movement of the turret in the tool changing, and thus cannot solve the problem due to the swinging movement of the turret in the tool changing.